Explain that each Spotlight should contain a Grid

packages/css/src/components/spotlight/README.md

@@ -7,6 +7,7 @@ Emphasizes a section on a page through a distinctive background colour.
 ## Guidelines
 
 - Display the Spotlight at the entire width of the [Screen](/docs/components-layout-screen--docs); do not position it on the [Grid](/docs/components-layout-grid--docs).
+- Add a Grid inside the Spotlight to add whitespace around the content, even for a single element.
 - The default background is purple, but the colours can be chosen freely – they do not convey a meaning or theme in itself.
 - Refer to [this overview on Stijlweb](https://amsterdam.nl/stijlweb/basiselementen/kleuren/#PagCls_15671872) to determine whether you can use black or white text on the background colour of your choice.